The balancing of AC (alternating current) bridges is a process that is critical in automated measurement and sensing systems, such as those used to measure/sense small changes in inductance/resistance. In addition, AC bridges of various forms have been utilized in various measurement and sensing systems, such as automatic testing systems, which are used to monitor such inductance/resistance changes.
However, such AC bridge circuits suffer from numerous technical problems. The primary problem of such bridge circuits is that of obtaining a minimum voltage and minimum phase at a middle point of the AC bridge circuit itself. In order to achieve a minimum voltage/phase at the middle point of the AC bridge, the AC bridge must be balanced, using various methods and techniques. For example, iterative methods to minimize the middle point voltage have been used. In other methods, the minimum point voltage is obtained by performing a sequence of complex computations that use a few, accurately sampled data points. With regard to the iterative method, the minimization of the middle-point voltage is achieved by computational steps performed by a computer based on a sequence of steps, which often results in the performance of many steps, which results in a slow convergence. Digital AC bridges that utilize a computer control system to carry out such iterative methods have also been developed. These digital AC bridges also provide advantages over that of conventional AC bridges, by providing measurements that have high accuracy, reproducibility, reliability, and flexibility. For example, such digital AC bridges may utilize a microprocessor that executes a least mean square (LMS) adaptive algorithm in an iterative manner to balance the bridge. However, while the LMS method is effective in balancing the AC bridge, the accuracy of the AC bridge balancing may be further improved by employing an intelligent neuro-fuzzy-based LMS module.
Iterative balancing methods, such as the LSM method, however, can be very slow as more computations are required for each step. To overcome the drawbacks of the iterative method, a non-iterative approach has also been investigated. Such non-iterative methods are desirable, as they speed-up the operation of the controller used to minimize the middle-point voltage by using Fourier coefficients of an out-of-phase voltage from the AC bridge. However, such non-iterative methods require a complicated digital signal processing (DSP) core or computational unit to carry out the complex computations and to perform the accurate data sampling that is required. As such, existing methods for balancing an AC bridge generally require highly complex computing systems, or perform balancing operations that are unacceptably slow.
Therefore, there is a need for a fast, automatic balancing AC bridge, which allows the AC bridge to measure/sense small inductance changes. In addition, there is a need for a system and method for a fast, automatic balancing AC bridge, which adds a synthetic phase offset to improve the accuracy of the phase measurement that is performed to balance the AC bridge. Furthermore, there is a need for a method for fast, automatic balancing of an AC bridge, which is based on trigonometric functions or formulas. Additionally, there is a need for a fast, automatic balancing AC bridge, whereby the balance parameters used to balance the AC bridge are analytically computed by a computer or any other suitable processing unit.